Re: [PATCH 03/13] x86/HV: Add new hvcall guest address host visibility support

[Tianyu Lan]

Hi Dave:
     Thanks for your review.

On 7/28/2021 11:29 PM, Dave Hansen wrote:
> On 7/28/21 7:52 AM, Tianyu Lan wrote:
> > @@ -1986,7 +1988,9 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
> >   	int ret;
> >   
> >   	/* Nothing to do if memory encryption is not active */
> > -	if (!mem_encrypt_active())
> > +	if (hv_is_isolation_supported())
> > +		return hv_set_mem_enc(addr, numpages, enc);
> > +	else if (!mem_encrypt_active())
> >   		return 0;
>
> __set_memory_enc_dec() is turning into a real mess.  SEV, TDX and now
> Hyper-V are messing around in here.
>
> It doesn't help that these additions are totally uncommented.  Even
> worse is that hv_set_mem_enc() was intentionally named "enc" when it
> presumably has nothing to do with encryption.
>
> This needs to be refactored.  The current __set_memory_enc_dec() can
> become __set_memory_enc_pgtable().  It gets used for the hypervisors
> that get informed about "encryption" status via page tables: SEV and TDX.
>
> Then, rename hv_set_mem_enc() to hv_set_visible_hcall().  You'll end up
> with:
>
> int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
> {
> 	if (hv_is_isolation_supported())
> 		return hv_set_visible_hcall(...);
>
> 	if (mem_encrypt_active() || ...)
> 		return __set_memory_enc_pgtable();
>
> 	/* Nothing to do */
> 	return 0;
> }
>
> That tells the story pretty effectively, in code.

Yes, this is good idea. Thanks for your suggestion.

> > +int hv_set_mem_enc(unsigned long addr, int numpages, bool enc)
> > +{
> > +	return hv_set_mem_host_visibility((void *)addr,
> > +			numpages * HV_HYP_PAGE_SIZE,
> > +			enc ? VMBUS_PAGE_NOT_VISIBLE
> > +			: VMBUS_PAGE_VISIBLE_READ_WRITE);
> > +}
>
> I know this is off in Hyper-V code, but this just makes my eyes bleed.
> I'd much rather see something which is less compact but readable.

OK. Will update.

> > +/* Hyper-V GPA map flags */
> > +#define	VMBUS_PAGE_NOT_VISIBLE		0
> > +#define	VMBUS_PAGE_VISIBLE_READ_ONLY	1
> > +#define	VMBUS_PAGE_VISIBLE_READ_WRITE	3
>
> That looks suspiciously like an enum.

OK. Will update.